There has long been a need for a very-low-power wakeup system that can be used in wireless sensor networks for secure asset and site protection. In other contexts as well, there has been a need for very-low power devices suitable for the long-term monitoring of infrequent events. In the medical field, for example, a very-low-power pulse monitor would be useful for detecting incidents of cardiac arrhythmia.
Piezoelectric detectors based, e.g., on thin-film aluminum nitride (AlN) have shown promise for sensing mechanical deformations without significant power consumption (other than for signal conditioning). However, there remains a need for highly sensitive and frequency-selective detectors suitable for long-term monitoring. Until now, the potential of piezoelectric detectors for such applications has not been fully exploited.